It was down to technical problems which it looks like (hopefully) they have fixed.

Nats spokesman Paul Haskins told BBC Radio's Good Morning Scotland programme: "We've had a technical problem overnight with interference with some of our radio frequencies which we use to speak to aircraft.

"It only affects some parts of Scottish airspace and flights from and to some Scottish airports but there may be delays as a result this morning.

"We have identified the cause and isolated the problem and the situation is now improving."

Transport minister Derek Mackay said: "There was a technical issue that has been rectified and addressed, however there are knock-on consequences to the airlines.